The GUID Partition Table ( GPT) is a standard for the layout of partition tables of a physical computer storage device, such as a hard disk drive or solid-state drive, using universally unique identifiers, which are also known as globally unique identifiers (GUIDs). Negative LBA addresses indicate a position from the end of the volume, with −1 being the last addressable block. The corresponding partition entries are assumed to be located in LBA 2–33. In this example, each logical block is 512 bytes in size and each entry has 128 bytes. The layout of a disk with the GUID Partition Table.